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Hot tub room

I have a customer who enclosed his hot tub in a wooden frame room on the patio of his home. 16' by 19' room, 10' high at the peak, 7' sidewalls. Open stud walls, only source of heat is a portable 110 volt propane heater as needed. He does not plan to insulate, just wants to vent the moisture out of the room. When he opens the lid on the hot tub, moisture drips off the joists.
He does not plan to use any other source of heat in the room.
We can purchase a humidistat-controlled fan easily enough.
How do I properly size this fan?
Is it smarter to vent thru the peak or should I place it about 6.5' off the floor near the hot tub?
How do I provide makeup air or is leakage thru the studs & windows going to be sufficient?
Thanks,
Rick

How can the exhaust fan be to big or small if its controlled by humidistat? It runs as long as it needs to. How can you ever keep the joists from sweating if the room is always cold and the he pops the top on that 102 degree tub? I would say any size fan would be temporarily overwhelmed.

Why did he enclose it? I would guess to use it in the colder weather. So since he enclosed it....it's trapping the heat (which is what he wanted), but also moisture. So now he wants to ventilate to get rid of the moisture build up....so you need more air exchanges. More air exchanges is going to drop the temp of the space. And round and round we go.

I have built an indoor H-Tub Room with roman tile floor, heavily insulated 6" walls, heated and air conditioned. The trick to keeping it from molding, sweating to long, and smelling like a bromine gym locker is high maintenance at the tub period. Drain and start over weekly with new water every week like a religion! Never try leaving the tub water conditioned as if outside and get a month out of it, it "will" ruin the room from then on. One must have at least 2 x 4 ft outside air coming in at the time of starting the tub and at least 1/2 hr or more after being done and the cover back on. One must have at least 350 CFM exhaust air going as well. Mine has been in service indoors connected to the home central system and I have zero issues so far!